Automatically growing lists in Python

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Sure it’s possible, you just have to use a subclass of list to do it.

class GrowingList(list):
    def __setitem__(self, index, value):
        if index >= len(self):
            self.extend([None]*(index + 1 - len(self)))
        list.__setitem__(self, index, value)

Usage:

>>> grow = GrowingList()
>>> grow[10] = 4
>>> len(grow)
11
>>> grow
[None, None, None, None, None, None, None, None, None, None, 4]

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